As an operation switch for various devices, there is a touch switch using a capacitive touch sensor. A touch (for example, a touch of a human body such as a human finger) for the touch switch is detected as follows. A capacitance value at the time when the human body (for example, a finger) does not touch an electrode of the touch sensor is set as a reference value, and it is determined whether there is a touch based on a result (that is, a change in capacitance value) of comparing the reference value with a detected value of a capacitance of the touch sensor.
The capacitive touch sensor may cause unintended operation, that is, malfunction due to an influence of external radio noise. In order to prevent the malfunction, an immunity measure to eliminate the influence of noise as much as possible has been variously proposed. For example, Patent document 1 discloses a technique for detecting environmental radio noise with the use of a dummy electrode (a dummy sensor) to prevent erroneous determination on a touch electrode (a touch sensor). In this technique, the dummy sensor is disposed at a distance apart from the touch sensor so as not to affect the touch operation on the touch sensor. When the touch operation (a change in the capacitance value) on the dummy sensor is detected, a determination that operation on the touch sensor is present may be discarded.
The inventor of the present application has found the following regarding the touch detection apparatus and the vehicle navigation apparatus.
The touch sensor may malfunction due to not only an influence of the external radio noise but also a user's unintentional touch. Such malfunction may easily occur in a layout where another operating unit (for example, a push switch, an operation knob) is disposed at a position extremely close to a switch using the touch sensor. In this layout, when the user attempts to operate the operation portion located in the vicinity of the touch sensor, the user's finger may unintentionally touch the touch switch. In this case, unintentional erroneous operation may be performed. The malfunction caused by the user's unintentional touch cannot be prevented by the immunity measure.